Valve assembly and airconditioning system including same

ABSTRACT

A valve assembly for controlling the flow of a fluid between a plurality of ports including at least one high pressure port and one low pressure port, includes: a base mounting the plurality of ports; and a valve member rotatable to a selected operational position with respect to the base. The control face of the valve member is formed with a low pressure cavity in the central region, and with an annular high pressure cavity in the outer region completely circumscribing the low pressure cavity. Such an arrangement produces a balanced valve construction which permits the valve member to be selectively rotated to the selected operational position, or to any intermediate position, while substantially isolating the high pressure from the low pressure in all its positions. This permits the valve assembly to be used not only as conventional change-over valve in an air conditioning system to select either a heating mode or cooling mode of operation, but also as a control valve to perform one or more additional control functions, e.g. for temperature or output control purposes, in any operational positions of the valve member.

CROSS REFERENCE TO OTHER APPLICATIONS

[0001] This application is a continuation of U.S. patent applicationSer. No. 09/489,806 filed on Jan. 24, 2000, which is a continuation inpart of U.S. application Ser. No. 09/096,563 filed on Jun. 12, 1998 nowU.S. Pat. No. 6,076,365.

FIELD OF THE INVENTION

[0002] The present invention relates to valve assemblies for controllingthe flow of a fluid between a plurality of ports. The invention isparticularly useful as a four-way change-over valve assembly in an airconditioning system, and method, for selectively operating the systemaccording to a cooling mode or a heating mode, and is therefor describedbelow particularly with respect to that application, but it will beappreciated that the invention and features thereof could alsoadvantageously be used in many other applications.

BACKGROUND OF THE INVENTION

[0003] Four-way change-over valves presently used in air conditioningsystems have to accommodate very large pressure differentials, in theorder of 30 atmospheres or more. Such high pressure differentials makeit difficult to assure that the valve will not leak in its high pressuresection, while at the same time to permit change-over from one operatingcondition to another by the use of a relatively small amount of force.Van Allen U.S. Pat. No. 2,855,000 addresses this problem in a simplemanually-operated change-over valve providing only a simple change-overoperation. Other four-way change-over valves hereto developed have beenof a relatively complicated and expensive construction, as shown forexample in U.S. Pat. Nos. 5,462,085 and 5,507,315.

[0004] Existing air-conditioning systems are also subject to a number ofother problems. One problem is frosting or icing, which can occur whenthe system is operated in the heating mode (during the winter) or in thecooling mode (during the summer). Should frosting occur in the heatingmode, the usual remedy is to change-over to the cooling mode in order toheat the outside coil, and also to shut-off the fan. As a result,considerable energy is lost, and the heating time and the heatingcapacity are reduced. Should frosting occur in the cooling mode, theusual remedy is to shut-off the compressor and/or to stop or change thespeed of the fan, which thereby also involves a loss of energy, time,and cooling capacity. Moreover, interrupting the operation of thecompressor is unhealthy to the compressor and requires waiting severalminutes before its operation can be resumed. Further, to preventfrosting in the cooling mode, the system is generally designed tooperate the evaporator at a temperature significantly above freezing,e.g. about 7° C., to accommodate changes in the outside temperature;this also reduces the efficiency and cooling capacity of the system ascompared, for example, when operating at a temperature closer to 0° C.

[0005] Another problem involved in present air-conditioning systems isin reducing the cooling or heating capacity of the system, e.g. when thevolume of the enclosed space to be cooled or heated is significantlyreduced as by shutting off rooms, etc. The present air-conditioningsystems are generally merely turned-off in order to reduce the coolingor heating capacity. However, this manner of reducing the capacity alsoreduces the overall efficiency of the system and wastes energy.Moreover, frequent interruption of the system tends to reduce the usefullife of the compressor and the fan.

OBJECTS AND SUMMARY OF THE INVENTION

[0006] An object of the present invention is to provide an improvedvalve assembly which can accommodate large pressure differentialswithout leakage, which can be actuated from one operating condition toanother by the use of a relatively small amount of force, and which canprovide other controls, particularly with respect to temperature and/oroutput. Another object of the present invention is to an airconditioning method and system including a valve assembly which may beused not only as a normal change-over valve for changing-over theoperation of the system from cooling to heating and vice versa, butwhich also may be used as a control valve for performing many controlfunctions within each operational mode, including preventing frosting,defrosting, reducing system capacity when required, etc., in a moreefficient manner than in the present air-conditioning systems.

[0007] According to one aspect of the present invention, there isprovided a valve assembly for controlling the flow of a fluid between aplurality of ports including at least one high pressure port and one lowpressure port, comprising: a base mounting the plurality of ports; and avalve member rotatable to a plurality of operational positions withrespect to the base. The valve member has a control face facing the baseto control the flow of fluid between the ports according to the positionof the valve member with respect to the base, and an opposite facefacing away from the base. The control face of the valve member isformed with a low pressure cavity in the central region thereof, andwith an annular high pressure cavity in the outer region thereofcompletely circumscribing the low pressure cavity.

[0008] According to further features in the described preferredembodiments, the valve assembly further comprises a slow-acting vent forapplying high pressure from the high pressure cavity to the oppositeface of the valve member, when the valve member is in an operationalposition, to firmly press the valve member into sealing contact with thebase, and thereby to isolate the high pressure cavity from the lowpressure cavity; a pilot valve which is normally closed but selectivelyopenable to release the high pressure applied to the opposite face ofthe valve member, and thereby to enable the valve member to be moved toanother operational position; and a passageway from the annular highpressure section of the valve member to the opposite face of the valvemember to maintain the control face of the valve member sufficientlyclose to the base to substantially isolate the high pressure cavity fromthe low pressure cavity also when the pilot valve is open and is movedto another operational position. The latter isolation is not completebecause of a thin air cushion produced by the high pressure cavitybetween the base and valve member completely around the valve member,but is sufficient to permit the valve also to be used as a control valveto perform a number of control functions, particularly for temperaturecontrol and/or output control purposes.

[0009] As will be described below, a valve assembly constructed inaccordance with the foregoing features provides a high degree ofprotection against leakage from its high pressure section when the valveassembly is in an operating condition, permits the valve to bechanged-over to another operating condition by the application of arelatively small amount of force, and further permits the valve, to beused to perform a number of important control functions when in eitheroperating position. The valve assembly can therefore be constructed in asimple, inexpensive and compact form, as compared to previousconstructions, and is particularly useful in air-conditioning systems tobe operated according to a cooling mode in the summer and a heating modein the winter.

[0010] According to another aspect of the present invention, therefore,there is provided an air-conditioning system for air-conditioning anenclosed space by compressing and expanding a fluid, comprising: aninside heat exchanger to be located within the enclosed space; anoutside heat exchanger to be located outside the enclosed space; acompressor having a low pressure side and a high pressure side; and achangeover valve. The change-over valve includes: a base having a lowpressure port connected to the low pressure side of the compressor, anda high pressure port connected to the high pressure side of thecompressor; a valve member rotatable with respect to the base; a rotarymotor drive for driving the valve member; and a controller forcontrolling the rotary motor drive to selectively drive the valvemember; (a) to a first position connecting the low pressure port to theinside heat exchanger and the high pressure port to the outside heatexchanger to define a low pressure section including the inside heatexchanger for using the fluid to cool the enclosed space; (b) to asecond position connecting the high pressure port to the inside heatexchanger, and the low pressure port to the outside heat exchanger, tothe outside heat exchanger, to the define a high pressure sectionincluding the inside heat exchanger for using the fluid to heat theenclosed space. The controller also controls the rotary motor drive forselectively driving the valve member to at least one further position,in addition to and preferably between the first and second positions.The valve member is constructed to maintain the high pressure sectionsubstantially isolated from the low pressure section, and to perform atleast one additional control function, when the valve is driven to thefurther position.

[0011] One described additional function is to shunt a part of the fluidfrom the high pressure port to the low pressure port to thereby controltemperature within the system without interrupting the compressor.Another described additional function is to restrict the effectivecross-sectional area of the low pressure port with respect to theheat-exchanger connected to it, to thereby control the output of thesystem without interrupting the operation of the compressor. A furthercontrol function is to selectively open and close the pilot valve, notonly for making a change-over operation, but also for controllingleakage from the high pressure port to the low pressure port fortemperature control purpose in any position of the valve.

[0012] Such an air-conditioning system can therefore be operated toperform many diverse control functions, including preventing frosting oroverheating, reducing system capacity, etc., in a continuous, periodic,when-required manner. This permits the air-conditioning to be designedfor maximum efficiency and to be continuously controlled according tochanging conditions.

[0013] According to a still further aspect of the present invention,there is provided a method of air-conditioning an enclosed spaceproviding the advantages described above.

[0014] Further features and advantages of the invention will be apparentfrom the description below.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The invention is herein described, by way of example only, withreference to the accompanying drawings, wherein:

[0016]FIG. 1 is an exploded 3-dimensional view illustrating a preferredform of valve assembly constructed in accordance with the presentinvention;

[0017]FIG. 2 is an exploded 3-dimensional view illustrating only thebase-mounted ports and the opposite side of the valve member from thatshown in FIG. 1;

[0018]FIG. 3 is a sectional view of the valve assembly of FIG. 1 inassembled condition;

[0019]FIG. 4a and 4 b illustrate, along section lines IV-IV, FIG. 3, twopositions of the coupling disk with respect to the valve member in FIG.1;

[0020]FIGS. 5a and 5 b illustrate, along section lines V-V, FIG. 3, thetwo normal operational positions of the valve member in the valveassembly of FIG. 1;

[0021]FIGS. 6a and 6 b illustrate an air conditioning system includingthe valve assembly of FIG. 1, with the valve member in the cooling modeposition and heating mode position, respectively, of FIGS. 4a and 5 b;

[0022]FIGS. 7 and 8a-8 c illustrate a variation in the construction ofthe coupling disk and the valve member;

[0023]FIG. 9 schematically illustrates an electrical control system forcontrolling the rotary motor in the valve assembly to provide not onlychange-over from one operation to another, but also to providecontrolled leakage or bleeding from the high-pressure section to thelow-pressure section, in order to prevent frosting or to defrost withoutinterrupting the operation of the system;

[0024]FIGS. 10a-10 f are views, similar to those of FIGS. 5a and 5 b,illustrating how controlled leakage may be produced to prevent frostingor to defrost;

[0025]FIGS. 11a-11 c are views similar to those of FIGS. 10a-10 cillustrating how the valve assembly may be operated to reduce capacitywithout interrupting the operation of the system;

[0026]FIGS. 12a-12 c corresponds to FIGS. 8a-8 c but illustrate amodification wherein the valve assembly is operated to perform a controlfunction without interrupting the operation of the system;

[0027]FIGS. 13 and 14 illustrate two further applications of the valveassembly of the present invention;

[0028]FIG. 15 is an exploded three-dimensional view illustrating anotherpreferred form of valve assembly constructed in accordance with thepresent invention;

[0029]FIGS. 16a and 16 b are three-dimensional views illustrating thetwo opposite sides of the valve member in the assembly of FIG. 15;

[0030]FIG. 17a is a bottom view illustrating the control face of thevalve member in the valve assembly of FIG. 15;

[0031]FIG. 17b is a top view illustrating the base-mounted portsco-operable with the valve member in the valve assembly of FIG. 15;

[0032]FIGS. 18a and 18 b illustrate an air-conditioning system includingthe valve assembly of FIG. 15, with the valve member in the cooling modeposition and heating mode position respectively;

[0033]FIGS. 19 and 19a diagrammatically illustrate the valve assembly ofFIG. 15 in its normal cooling position;

[0034] FIGS. 20-23 diagrammatically illustrate the valve assembly in itscooling mode but at different positions to control a pair of shuntinglines for temperature control purposes;

[0035]FIGS. 20a, 20 b-23 a, 23 b illustrate two optional controls of thepilot valve in each of the valve positions illustrated in FIGS. 20-23respectively;

[0036] FIGS. 24-27 and 24 a-27 b are views corresponding to FIGS. 19-23b but showing the valve member in its heating mode position;

[0037]FIG. 28 is a top view illustrating the base-mounted ports ofanother preferred form of a valve member of a valve assembly constructedin accordance with the present invention;

[0038]FIGS. 29a and 29 b illustrate an air-conditioning system includingthe valve assembly of FIG. 28, in the cooling mode position and heatingmode position respectively;

[0039]FIGS. 30a-30 c diagrammatically illustrate the valve assembly ofFIG. 28, in its cooling mode at different positions; and

[0040]FIGS. 31a-31 c diagrammatically illustrate the valve assembly ofFIG. 28, in its heating mode at different positions.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

[0041] The valve assembly illustrated in FIGS. 1-6 b serves both as afour-way change-over valve for an air conditioning system, to operatethe system according to either a cooling mode or a heating mode, andalso as a control valve for performing any one of a number of controlfunctions in either mode. The air conditioning system, asdiagrammatically illustrated in FIGS. 6a and 6 b, includes a compressor2; an inside heat-exchanger or coil 4 (acting as an evaporator in thecooling mode); an outside heat-exchanger or coil 6 (acting as acondenser in the cooling mode), and a valve assembly 8, having a lowpressure port LP_(C) connected to the inlet of the compressor 2, and ahigh-pressure port HP_(C) connected to the outlet of the compressor 2.The valve assembly 8 has two further ports HX_(I) and HX_(O) to beconnected to ports LP_(C) and HP_(C) according to the specific mode ofoperation of the air conditioning system. Thus, FIG. 6a illustrates thecooling mode of operation, wherein port HX_(I) connects the low pressurefrom port LP_(C) to the inside heat-exchanger 4, and port HX_(O)connects the high pressure from port HP_(C) to the outsideheat-exchanger 6; whereas FIG. 6b illustrates the heating mode ofoperation wherein port HX_(O) connects the low pressure from port LP_(C)to the outside heat-exchanger 6, and port HX₁ connects the high pressurefrom port HP_(C) to the inside heat-exchanger 4.

[0042] The construction of valve assembly 8 is more particularlyillustrated in FIGS. 1-3. It includes a base 10 mounting the four portsLP_(C), HP_(C), HX_(I), HX_(O), which ports are connected by linesL₁-L₄, respectively, to the compressor 2, inside heat exchanger 4, andoutside heat-exchanger 6. Valve assembly 8 further includes a valvemember, generally designated 20, which is rotatable to two operationalpositions to control the flow of the gas between the four ports toproduce the cooling and heating modes of operation. Valve member 20 isrotated to its two operational positions by a drive, generallydesignated 30, and a coupling member or disk, generally designated 40.

[0043] Valve member 20, coupling disk 40, and a part of the drive 30,are all enclosed within a housing 50, which is hermetically sealed tothe base 10. The remaining elements of the drive 30 are enclosed withina second housing 60 secured to the upper end of housing 50.

[0044] The base 10, which forms the bottom wall of housing 50, includesa plurality of holes defining the four ports. Port LP_(C), connected byline L₁ to the low pressure inlet of compressor 2 (FIGS. 6a, 6 b), is ofthe largest cross-sectional area, and is located centrally of base 10.Port HP_(C), connected by line L₂ to the high pressure outlet ofcompressor 2, is located adjacent to the outer periphery of base 10.Port HX_(I) connected by line L₃ to the inside heat-exchange 4, and portHX_(O) connected by line L₄ to the outside heat-exchanger 6, are locatedon the outer periphery of base 10 on opposite sides of port HP_(C).

[0045] Base 10 further includes a stop 11 on its inner face. This stopcooperates with the valve member 20 to locate that member in its twooperational positions, one producing a cooling mode of operation, andthe other producing a heating mode of operation.

[0046] As shown particularly in FIG. 2, the control face of valve member20 (that facing base 10) includes two closed-loop, concentric ribformations 21, 22. Rib formation 21 is an inner closed loop centrally ofthe control face of valve member 20; it defines an inner low pressurecavity or section 23 in the central region of that face which is incommunication with the low pressure port LP_(C) in base 10. Ribformation 22 is an outer, annular closed loop; it defines with inner ribformation 21, an outer high-pressure section completely circumscribingthe inner low-pressure section 23 and in communication with the highpressure port HP_(C) of base 10. High-pressure section 24 includes twoside portions 24 a, 24 b, joined together by passageways 24 c, 24 d, soas to completely surround the low-pressure section 23.

[0047] For purposes to be described below, a small hole 25 is formedthrough the high pressure section 24 of valve member 20, and a largerhole 26 is formed through its low pressure section 23.

[0048] The opposite face of valve member 20 (shown in FIG. 1) faces thecoupling disk 40. This face includes an outer peripheral wall 27 formedwith two cam surfaces 28, which extend radially inwardly of the valvemember at diametrically-opposite locations thereon, and a slot 29extending through an arc of approximately 60°. As will be described moreparticularly below, cam surfaces 28 and slot 29 cooperate with couplingdisk 40 to couple the valve member 20 to the drive via a lost-motioncoupling enabling the coupling disk to be rotated a small amount withoutrotating the valve member.

[0049] As indicated earlier, drive 30 is divided into two sections. Onesection includes parts enclosed within housing 50 containing the valvemember 20 and the coupling disk 40; whereas the other section isexternally of housing 50 and is enclosed within the second housing 60secured to the upper end of housing 50.

[0050] The parts of drive 30, located externally of housing 50 (andwithin housing 60) include a motor 31, preferably a step motor, having arotary shaft 32 for rotating a disk 33. Disk 33 carries a pair ofpermanent magnets 33 a, 33 b on opposite sides of the disk anddiametrically aligned with its axis of rotation.

[0051] The parts of drive 30 located internally within housing 50include another disk 34 rotatably mounted on a pin 35 secured to arotatable end disk 35 a. Disk 34 carries a pair of permanent magnets 34a, 34 b diametrically aligned with the axis of rotation of disk 34.Permanent magnets 34 a, 34 b on disk 34 within housing 50 are of thesame circular configuration as permanent magnets 33 a, 33 b on disk 33within housing 60, and are adapted to be axially aligned with thosemagnets to produce a magnetic coupling between the two disks so that therotation of disk 33 externally of housing 50 produces a correspondingrotation of disk 34 within housing 50.

[0052] The rotation of disk 34 within housing 50 is transmitted, viacoupling disk 40, to the valve member 20 by means of a drive gear 36carried by disk 34, and a step-down transmission 37 coupled to thecoupling disk 40.

[0053] Step-down transmission 37 is of a two-stage planetary-gear typebest seen in FIG. 3. It includes an outer housing 37 a formed with acentral opening for receiving drive gear 36 of disk 34, a ring gear 37 bfixed to the inner face of housing 37 a, and two stages 38 a, 38 b ofplanetary gears cooperable with ring gear 37 b. The first stage 38 aincludes three planetary gears meshing with ring gear 37 b for rotatinga disk 39. Disk 39 is in turn fixed to a drive gear 39 a meshing withthe three planetary gears of the second stage 38 b, the latter gearsalso meshing with ring gear 37 b. The arrangement is such that fastrotation of disk 34 produces a slow rotation of disk 39, and itsplanetary gear 38 b of the step-down transmission 37. A projection 50 aon the inner face of housing 50, received within a corresponding recessin the transmission housing 37 a, prevents rotation of the transmissionhousing during the rotation of the planetary gears.

[0054] Coupling disk 40 is formed with three stems 41 received withinthe openings in the three second-stage planetary gears 38 b such thatthe slow rotation of disk 39 at the output end of the step-downtransmission 37 produces a slow rotation of the coupling disk 40. Thisrotary movement of coupling disk 40 is transmitted to the valve member20 in a yieldable manner by a pair of radially-extending, spring-urgedcoupling pins 42, 43, engaging cam surfaces 28 on the inner surface ofthe annular wall 27 of the valve member 20, as best seen in FIG. 1.

[0055] Coupling disk 40 not only couples the valve member 20 to thedrive, but also cooperates with the large hole 26 for controlling thefluid pressure applied to the valve member. For the later purpose,coupling disk 40 is provided with a pair of pilot valve elements 44,45,each adapted to cover or uncover the large hole 26 according to theposition of coupling disk 40 with respect to the valve member 20.Coupling disk 40 further includes a depending pin 46 received withinslot 29 in valve member 20, limiting the rotation of the coupling disk40 with respect to the valve member.

[0056] The change-over operation, wherein the air-conditioning system ischanged-over from a cooling mode (in the summer) to a heating-mode (inthe winter), or vice versa, will now be described particularly withreference to FIGS. 4a-6 b.

[0057] It will be assumed that the valve member 20 is in the positionillustrated in FIG. 5a, which produces a cooling mode of operation ofthe air conditioning system as illustrated in FIG. 6a. In thisoperational position of the valve member 20, the low-pressure from portLP_(C) (connected to the low-pressure side of compressor 2) is connectedto port HX_(I) leading to the inside heat-exchanger 4, and thehigh-pressure from port HP_(C) (connected to the high-pressure side ofthe compressor) is connected to port HX_(O) leading to the outsideheat-exchanger 6, thereby producing a cooling mode of operation as shownin FIG. 6a.

[0058] When the valve member is in the operational position of FIG. 5a,the high-pressure appearing in the high-pressure section 24 of the valvemember is transmitted via the small hole 25, acting as a slow-actingvent, to the opposite side of the valve member (the side illustrated inFIG. 1). Since the surface area at this side of the valve member is muchlarger than the high-pressure surface area 24 at the opposite side ofthe valve member, this high-pressure applied via small hole 25 iseffective to firmly press valve member 40 against base 10, therebyproducing a tight seal against leakage of gas.

[0059] When it is desired to change the operational position of thevalve member in order to produce a heating mode of operation asillustrated in FIG. 6b, motor 31 of the drive is energized to rotatedrive disk 33, which as described above, is externally of housing 50.However, the magnetic coupling produced by permanent magnets 33 a, 33 bon the external drive disk 33, and magnets 34 a, 34 b on the internaldrive disk 34, transmits the rotary motion of motor 31 to the internaldrive disk 34 via the step-down transmission 37 within housing 50. Therotary speed of drive disk 34 is thus reduced by the two-stage planetarygearing transmission of the step-down transmission 37, to rotatecoupling disk 40, coupled to the second stage planetary gearing by stems41, at a relatively low speed. For example, each stage of the two-stagetransmission 37 could produce a step-down ratio of 25:1 so that thestep-down transmission ratio of the complete transmission 37 is 50:1.

[0060] In the initial position of coupling disk 40 (as shown in FIG. 4abefore it begins to rotate), its pin 46 is in one end of slot 29(FIG. 1) of the valve member 20. Also, one of its pilot valve elements44,45, closes the large hole 26 in the valve member 20, to produce thehigh-pressure sealing effected by the small hole 25, as described above.

[0061] Immediately upon the initial movement of the coupling disk 40,and before the valve member 20 begins to move, the large hole 26 in thevalve member is uncovered by the respective pilot valve element 44,45.This immediately releases the high pressure pressing valve member 20against base 10, thereby enabling the valve member to be easily rotatedby coupling disk 40.

[0062] Rotation-of coupling disk 40 causes the spring-urged pins 42, 43of the coupling disk to move relative to valve member 20 (FIG. 4b) untilthey engage cams 28 on the inner surface of peripheral wall 27 of thevalve member and thereby rotate the valve member to the operationalposition illustrated in FIG. 5b. This position is determined by theengagement of stop 11 of base 10 with the opposite end of the outerhigh-pressure section 24 of the valve member. Stop 11 thus preventsfurther rotation of valve member 20 so that the coupling disk 40 nowrotates relative to the valve member to bring its other pilot valveelement 44,45, over the large hole 26, and thereby to reinstate thehigh-pressure seal applied to the valve member by the small hole 25. Thevalve member is thus now in the position illustrated in FIG. 5b,determined by pin 46 engaging the opposite end of slot 29, therebyproducing a heating mode of operation of the air conditioning system asillustrated in FIG. 6b.

[0063] In the illustrated construction, the above-described change-overoperation takes 1.0 to 1.5 seconds. However, may be slowed down ifdesired, by controlling the valve motor 31, e.g. to avoid sudden shocksto the air-conditioning system.

[0064] Whenever it is a desired to make a change-over to a cooling modeof operation, motor 31 is energized in the reverse direction, whereuponthe same sequence of events as described above occur to move the valvemember 20 back to the position illustrated in FIG. 5a, to therebyproduce a cooling mode of operation of the air conditioning system asillustrated in FIG. 6a.

[0065]FIGS. 7 and 8a-8 c illustrate a variation wherein the cam surfaces28 are in the form of curved elongated elements 128 having three camformations 128 a, 128 b, 128 c. Each cam formation 128 extends for anarc of about 120°. They are separated by slots 129 each of approximately60°, corresponding to arcute slots 29 (FIG. 1). In addition, thecoupling disk 40 is provided with two radial ribs 146 which move inslots 129 and thus serve the same function as pin 46 movable within slot29 in FIG. 1, as described above.

[0066] As shown particularly in FIGS. 8a-8 c, the spring-urged pins 43of coupling disk 40 operate with cam surfaces 128 a, 128 b, 128 c of thetwo cam elements 128 in the same manner as described above, first torelease the high sealing pressure applied to valve member 20, then torotate the valve member to its new operational position, and then torestore the high-sealing pressure applied to the valve member. Thus,when the valve member is precisely in an operational position, pilotvalve element 44 of the coupling disk, being precisely over largeopening 26 in the valve member (FIG. 8a), is closed, such that thehigh-sealing pressure is applied to the valve member as describe above.When the valve member is to be moved to a new operational position,coupling disk 40 is first rotated to displace pilot valve element 44away from opening 26 (FIGS. 8b, 8 c), thereby releasing the high sealingpressure, such that when pins 42, 43 engage the middle cam surface 128b, the coupling disk will rotate the valve member to its new operationalposition. It is stopped in this operational position by pin 11 asdescribed above, whereupon coupling disk 40 will continue to move,overcoming the middle cam surface 128 b until it reaches the end camsurface 128 c; at that position its other pilot valve element 45 nowcovers large opening 26 to thereby restore the high sealing pressure tothe valve member.

[0067] An important characteristic of the described valve assembly isthat it automatically maintains the valve member 20 very close to thebase 10, separated by a thin air cushion, all the time the valve memberis not precisely in one of its two operational positions. This closespacing is automatically self-regulated all the time the valve member isnot precisely in one of its operational positions by leakage from thecircular high pressure section 24 at the ribbed face of valve member 20to the opposite face of the valve member. Thus, should valve member 20tend to tilt or separate from base 10 at any point around thecircumference of the valve member, the so-produced space will cause thehigh pressure from the annular high pressure section 24 to be appliedvia this space to the opposite face of valve member 20, therebyrestoring the valve member to its close position with the base.

[0068] This regulated action of the valve member 20 thus produces a thinair cushion, which facilitates the change-over operation for changingfrom one operational mode to another. While this air cushion producessome leakage, it is relatively small such that the high-pressure sectionof the valve member is still substantially isolated from thelow-pressure section sufficiently to enable the valve assembly to servealso as a control valve and to perform many important control functionswithin an operational mode. Described below, for purposes of example,are anti-frosting or defrosting control, and output-reduction control,both of which may be performed by the described valve assembly in eitherof the two operational modes of the air-conditioning system and withoutinterrupting the operation of the air-conditioning system.

[0069]FIG. 9 diagramatically illustrates an electrical circuit forcontrolling the valve motor 31 of the valve assembly both for a modechange-over operation, and also for a control operation within one ofthe modes. The system illustrated in FIG. 9 includes a control circuitCC for controlling the valve motor 31; a mode selector MS for operatingthe system according to the cooling mode (in the summer), or the heatingmode (in the winter); a defrost selector DS for producing ananti-frosting or defrosting control operation within one of the twooperational modes; and an output selector OS for controlling the outputof the system without interrupting the operation of the system. Alsoillustrated in FIG. 9 is a temperature sensor TS which sensestemperature, e.g., the outside ambient temperature, and produces anoutput to the control circuit CC automatically controlling valve motor31 in order to prevent frost, or to defrost, in a very efficient mannerand without interrupting the operation of the system.

[0070] The described valve assembly enables the air-conditioning systemto be operated in order to prevent frosting, to defrost, or to provideother temperature controls, both in the cooling mode and the heatingmode. The manner in which this is accomplished is illustrated in FIGS.10a-10 f.

[0071] In FIGS. 10a-10 f, the ports LP_(C), HP_(C), HX_(I), HX_(O) arecorrespondingly marked as in FIGS. 5a and 5 b. However, the ribformation 21, which defines the inner low-pressure region 23 and theouter, annular high-pressure region 24, is not of even thickness asillustrated in FIG. 2, but rather of varied thickness as shown by thesection lines 121 in FIGS. 10a-10 f. This is preferable particularly forthe output-reduction control to be described below.

[0072]FIG. 10a illustrates the position of the rotary valve member 120with respect to the four ports in the base (10, FIG. 1) to produce acooling mode of operation as described above particularly with respectto FIG. 5a. Whenever it may be desired to prevent frosting, to defrost,or to provide other temperature controls, valve member 120 may be moved,via the coupling disk (40, FIG. 1) to produce a controlled leakage orbleeding between the high-pressure outer region 124 produced by thehigh-pressure port HP_(C), and the low-pressure central region 123coupled to the low-pressure port LP_(C), corresponding to the amount ofleakage desired. The leakage not only influences the pressure of the gasin each region but also influences the temperature in each region.

[0073]FIGS. 10b-10 e illustrate how this leakage may be increased, asdesired, until the second operational position, namely the heating mode,is reached as illustrated in FIG. 10f. It will be appreciated that thegreater the leakage, the greater will be the anti-frosting or defrostingresults.

[0074] This leakage to prevent frosting (or to defrost) may beautomatically controlled in response to the outside ambient temperatureby temperature sensor TS illustrated in FIG. 9. For example, when thesystem is operating according to the cooling mode, and the outsideambient temperature drops, this will be sensed by temperature sensor TSto automatically control, via circuit CC, the valve motor 31 to producea controlled leakage of high temperature gas to the region to be warnedin order to prevent frosting or to defrost.

[0075] This control may be a periodic one, wherein valve motor 31(FIG. 1) would be controlled to periodically move the valve member toone of the positions illustrated in FIGS. 10b-10 e and then back to itsnormal operating position. This periodic control of leakage may beeffected by periodically controlling the amplitude of the leakage (perFIGS. 10b-10 e), the time interval of each period of leakage, and/or thefrequency at which the leakage is effected. Such a control, may also becontinuous, wherein a continuous leakage could be provided having amagnitude depending on the output of the temperature sensor to preventfrosting. This leakage can also be produced manually by operatingdefrost selector button DS (FIG. 9), or automatically in response totemperature. Such an anti-frosting or de-frosting operation is easilypermitted by the described valve assembly without interrupting theoverall operation of the system since: (1) the valve motor 31 can beprecisely controlled by the control circuit CC; (2) since the valvemember may be easily rotated to any desired position with respect tobase 10; and (3) the regulated light contact, or very close spacing, ofthe valve member with respect to the base, whenever the valve member isnot in one of its operational positions, substantially isolates thehigh-pressure section from the low-pressure section sufficiently topermit this type of control.

[0076] An anti-frost or defrost control as described above provides anumber of important advantages. It enables the air-conditioning systemto be operated for maximum efficiency without danger of frosting. Italso permits the system to be operated continuously, and not to beinterrupted or reversed, thereby saving considerable energy, maximizingthe utilization of the air-conditioning system, and avoiding undesirableinterruption of the compressor.

[0077]FIGS. 11a-11 c illustrate how the novel valve assembly may bemodified to produce a desired output-reduction in the air-conditioningsystem without interrupting its operation. For example, air-conditioningsystems are normally designed for maximum efficiency at a predeterminedoutput, and if the needed output is to be reduced, e.g. because of adecrease in the space to be heated or cooled, it is usually necessary tointerrupt the operation of the system. However, such an operation of anormal air-conditioning system reduces its overall efficiency, wastesconsiderable energy, accelerates wear, etc., because of frequentinterruptions of the system.

[0078] The valve assembly of the present invention permits the output ofthe air-conditioning system, both in the cooling mode and in the heatingmode, to be reduced as desired without interrupting the operation of thesystem. This can be done, for example, by controlling the valve motor 31to produce a controlled reduction in the effective cross-sectional areaof the low-pressure port LPC exposed to the heat-exchanger connected toit. Thus, FIG. 11a illustrates the valve member 120 in a cooling-modeposition wherein its rib 121 fully opens the low-pressure port LPCexposed to the inside heat-exchanger port HXI, thereby producing 100%suction; FIG. 11b illustrates the valve member position wherein rib 121covers about 25% of the cross-sectional area of the low-pressure portLPC, thereby producing about 75% suction; and FIG. 11c illustrates thevalve member position wherein rib 121 covers about 75% of thecross-section area of the low-pressure port LP_(C) thereby producingabout 25% suction.

[0079] Such an output-reduction operation may also be performedperiodically, continuously, or as required by the motor control circuitCC controlling valve motor 31, as described above with respect to thetemperature control, and does not require interrupting the operation ofthe air-conditioning system.

[0080]FIGS. 12a-12 c are views corresponding to those of FIGS. 8a-8 cbut including slight modification of the valve member 120 with respectto the location of the cam elements 128, engageable by the spring-urgedpins 42, 43, to better assure that the coupling disk 40 will not move toa position causing its pilot valve elements 44, 45, to cover thelow-pressure large hole 26 in the valve member except when the valvemember is precisely in one of its two operational positions. Thus, thespring-urged pins 42, 43, engage the cam element high points 128 a, 128c only after a pilot valve element 44, 45 closes the low-pressure port26 to reapply the high sealing pressure against the valve member (FIG.12c).

[0081] The illustrated valve assembly may be used for performing othercontrol functions within either of the two operational modes. Forexample, the valve motor 31 may be controlled merely to periodicallymove coupling disk 40 sufficiently to cause its pilot valve elements 44or 45 to unseat large hole 26, and thereby to bleed-off a small amountof high-pressure, without actually moving valve member 20. Such anoperation may be desired to perform a small hot-gas bypass control asoften as may be necessary.

[0082] The illustrated valve assembly may also be used for controlling adifferent number of ports. FIG. 13 illustrates an example wherein thevalve assembly includes only three ports, namely a low-pressure port P₁,a high pressure point P₂, and a further port P₃ to selectively receiveeither the low pressure from port P₁ or the high pressure from port P₂.

[0083]FIG. 14 illustrates a valve assembly including five ports, ofwhich ports P₁-P₄ are the four ports described above (e.g. FIG. 2), thefifth port P₅ being provided to selectively apply high-pressure to theevaporator, for example, for defrosting or other control purposes.

[0084]FIG. 15 illustrates a valve assembly very similar to thatdescribed above with respect to FIGS. 1-3, and therefore in order tofacilitate understanding, corresponding parts have been identified bythe same reference numerals. The main differences between the twostructures appear in the base, and in the valve member, identified as210 and 220, respectively, in FIG. 15. FIG. 16a more particularlyillustrates the side of valve member 220 facing the coupling disk 40;FIGS. 16b and 17 a more particularly illustrate the side of the valvemember facing the base 210; and FIG. 17b more particularly illustratesthe base 210 cooperable with the valve member 220.

[0085] Base 210 mounts the same four ports LP_(C), HP_(C), HX_(I),HX_(O) as in FIG. 1, which ports are connected by lines (L₁-L₄, FIG. 1)to the compressor 2, the inside heat exchanger 4, and the outside heatexchanger 6 (FIGS. 18a, 18 b). Base 210 also includes a stop 211,corresponding to stop 11 in FIGS. 1-3 but of smaller diameter. Stop 211is straddled on its opposite sides by two additional ports, namely: ashunting port S_(I) connecting a shunt line 212 (FIGS. 18a, 18 b) to theinside heat exchanger 4, and a shunting port S_(O) connecting a secondshunt line 213 to the outside heat exchanger 6.

[0086] The control face of valve member 220, as illustrated particularlyin FIG. 17a, also includes an inner closed-loop rib 221 defining acentral low-pressure section 223, and an outer annular rib 222 defining,between it and rib 221, an outer, annular high-pressure section 224enclosing the inner low-pressure section 223. The two closed-loop ribs221 and 222 are specially shaped to cooperate with the ports in the base210, as will be described more particularly below.

[0087] As in the previously-described embodiments, valve member 220 alsoincludes a small hole 225 connecting the high pressure section 224 tothe opposite face of the valve member for applying high pressurethereto; and a larger hole 226 leading from the low-pressure section223, and co-operable with a pilot valve 244 on coupling disk 40, forreleasing the high pressure when it is desired to change-over the valvefrom one operational position to another.

[0088] The side of valve member 220 facing coupling disk 40 is somewhatdifferent in structure from that described above. As shown particularlyin FIG. 16a, this side of valve member 220 is formed with a peripheralrib 227 a, 227 b on each of its opposite sides, each formed with acentral recess 228. The two peripheral ribs extend for 120° to define a60° slot 229 a, 229 b, at each of its opposite sides.

[0089] As will be described below, recesses 228, serve as detents forreleasably receiving the two spring-urged pins 42, 43 of the couplingdisk 4 when the coupling disk is precisely in position wherein its pilotvalve 244 closes the large hole 226 in valve member 220; whereas slot229 a, 229 b cooperate with radial projections 246 a, 246 b in thecoupling disk 40 to rotate the valve member 220 to any desired positionafter the high-pressure applied to the valve member has been released byopening the pilot valve hole 226.

[0090]FIGS. 18a and 18 b illustrate the position of the valve member 220with respect to the base 210 for producing a cooling mode of operationand a heating mode of operation, respectively, corresponding to FIGS. 6aand 6 b in the earlier described embodiments. The valve illustrated inFIG. 15 may also be controlled in the manner described above withrespect to FIGS. 10a-10 f to produce any desired leakage control fromthe high pressure section to the low pressure section of the controlvalve for temperature control purposes, or as described above withrespect to FIGS. 11a-11 c to control the output of the system bycontrolling the cross-sectional area of the low-pressure port LP_(C)exposed to the respective heat exchanger.

[0091] The valve illustrated in FIG. 15, however, may be operated toperform further control functions. Thus, the provision of the twoshunting ports S_(I) and S_(O) in the base 210 permits the valve also tocontrol the shunting of gas to selected locations in the system via theshunting lines 212, 213 for temperature control purposes; also, thelost-motion construction of the side of valve member 220 facing thecoupling disk 40 enables the motor also to be used for selectivelyopening or closing the pilot valve PV (element 244 moveable with respectto opening 226) at any position of the valve member (i.e. in either ofthe two mode positions, or any intermediate position between them), e.g.to exert a moderate control of temperature or pressure whenever, and asoften as deemed necessary, without actually moving the valve member 220.

[0092] The foregoing operations are more particularly illustrated inFIGS. 19-24.

[0093]FIG. 19 illustrates a straight cooling mode, wherein the lowpressure port LP_(C) is coupled to the inside heat exchanger portHX_(I), and the high pressure port HP_(C) is connected to the outsideheat exchanger port HX_(O). In the position illustrated in FIG. 19,neither of the shunts S₁, S_(o) is active. FIG. 19a illustrates thenormal closed position of the pilot valve 244, i.e., closing hole 226,such that high pressure is applied via hole 225 to the opposite side ofthe valve member 220.

[0094]FIG. 20 illustrates the valve member 220 moved slightly(clockwise) to partially expose shunt port SI to the high pressurecavity 224, to thereby shunt a portion of the high pressure gas to theinside heat-exchanger 4. This may be desired, for example, to provide asmall hot-gas bypass in order to prevent freezing of the insideheat-exchanger. The valve member also slightly reduces thecross-sectional area of the inside heat-exchanger port HXI exposed tothe low pressure, but this is not significant here.

[0095]FIGS. 20a, 20 b illustrate that, in the valve position of FIG. 20,the pilot valve 244 may also be closed (FIG. 20a), or open (FIG. 20b) inorder to perform a small hot-gas bypass control, if so desired, withoutinterrupting the operation of the compressor.

[0096]FIGS. 21, 21a, and 21 b, illustrate similar conditions as FIGS.20, 20a, 20 b, but with the full cross-section of the shunting port S₁exposed to the high pressure section.

[0097]FIGS. 22, 22a, 22 b illustrate the condition wherein both shuntingports S_(I), S_(O) are blocked, but a smaller cross-sectional area ofthe inside heat-exchanger port HX_(I) is exposed to the low pressuresection, thereby further reducing the output of the air-conditioningsystem; and FIGS. 23, 23a and 23 b illustrate similar conditions buteven with a further reduction in the air-conditioning output system. Inboth cases, the cross-sectional area of outside heat-exchanger portHX_(O) exposed to the light pressure is also reduced, which therebyreduces the volume of the gas, and therefore this work load on thecompressor.

[0098] FIGS. 24-27 illustrate similar controls when the air-conditioningsystem is in the heating mode.

[0099] Reference is now made to FIGS. 28a-28 b, 29 a-29 b, 30 a-30 c and31 a-31, which illustrate another preferred embodiment of a valve memberforming part of a valve assembly, generally designated 300, constructedin accordance with the present invention.

[0100]FIG. 28a is a top view illustrating the base-mounted ports,generally designated 302 of a valve member 304 shown in FIG. 28b. FIGS.29a and 29 b illustrate an air-conditioning system including the valveassembly 300 of FIGS. 28a-28 b, in the cooling mode position and heatingmode position respectively;

[0101]FIGS. 30a-30 c diagrammatically illustrate the valve member 304,in its cooling mode at different positions. FIGS. 31a-31 cdiagrammatically illustrate the valve member 304, in its heating mode atdifferent positions.

[0102] Valve member 304 is similar to valve member 210 (shown in FIG.17b) and may be used in place of the valve member 210 within the valveassembly of FIG. 15. Elements having similar functions are similarlydesignated and will not be further described.

[0103] Base 302 mounts the same four ports LP_(C), HP_(C), HX_(I),HX_(O) as in FIG. 15, which ports are connected by lines (similar tolines L₁-L₄ of FIG. 1) to the compressor 2, the inside heat exchanger 4,and the outside heat exchanger 6 (FIGS. 29a, 29 b). Base 302 alsoincludes a stop 211, which is straddled on its opposite sides by twoexpansion ports, referenced S₂ and S₃ (FIGS. 29a, 29 b). Port S₂connects a shunt line 212 to the inside heat exchanger 4, and port S₃connects a second shunt line 213 to the outside heat exchanger 6. S₂ andS₃ are also connected to an expansion valve 315 (similar to element 244of FIG. 15). In addition, two additional ports, referenced S₄ and S₅(FIGS. 29a, 29 b) are provided. Port S₄ connects a third shunt line 314to the inside heat exchanger 4, and port S₅ connects a fourth shunt line316 to the outside heat exchanger 6.

[0104] The control face of valve member 304, as illustrated particularlyin FIG. 28b, includes a loop rib 306 defining a central low-pressuresection 308, and an outer, annular high-pressure section 310 and 312enclosing the inner low-pressure section 308. The loop rib 306 isspecially shaped to cooperate with the ports in the base 302, as will bedescribed more particularly below.

[0105] As in the previously-described embodiments, valve member 304 alsoincludes a small hole (similar to 225 in FIG. 16a) connecting the highpressure section 310 to the opposite face of the valve member forapplying high pressure thereto; and a larger hole (similar to 226 inFIG. 16a) leading from the low-pressure section 308, and co-operablewith a pilot valve 244 on coupling disk 40 (see FIG. 15), for releasingthe high pressure when it is desired to change-over the valve from oneoperational position to another.

[0106] The sides of valve member 304 facing coupling disk 40 are similarto that of valve member 220 but having a structure configured to valvemember 304, and will not be described further.

[0107]FIGS. 29a and 29 b illustrate the position of the valve member 304with respect to the base 302 for producing a cooling mode of operationand a heating mode of operation, respectively, corresponding to FIGS.18a and 18 b in the earlier described embodiments. The control of thevalve assembly 300 with the replacement of valve member 304 and the baseports 302 (in place of valve member 220 and the base ports 210 of FIG.15) is similar to the control operation described hereinabove.

[0108] The valve assembly 300 containing valve member 304 in conjunctionwith base 302 may be operated to perform several control functions. Asdescribed above with reference to FIGS. 18-27, the lost-motionconstruction of the side of valve member 304 facing the coupling disk 40enables the motor also to be used for selectively opening or closing theexpansion valve 315 at any position of the valve member (i.e. in eitherof the two mode positions, or any intermediate position between them),e.g. to exert a moderate control of temperature or pressure whenever,and as often as deemed necessary.

[0109] In addition, valve assembly 300 is provided with two additionalports S₄ and S₅ in the base 302 which permit the valve to also controlthe shunting of gas via the shunting lines 314, 316 for temperaturecontrol purposes.

[0110] The foregoing cooling and heating operations are moreparticularly illustrated in FIGS. 30a-30 c and 31 a-31 c, respectively.

[0111]FIG. 30a illustrates the cooling mode, wherein the low pressureport LP_(C) is coupled to the inside heat exchanger port HX_(I), and thehigh pressure port HP_(C) is connected to the outside heat exchangerport HX_(O). In the position illustrated in FIG. 30a, neither of theports S₄, S₅ are active but the expansion valve 315 is fully opened,with shunts S₂, S₃ open allowing the flow from shunt line 213 viaexpansion valve 315 and shunt line 212.

[0112]FIG. 30b illustrates the valve member 304 moved slightly(clockwise) to partially close shunt port S₂ to the high pressure cavity224.

[0113]FIG. 30c illustrates the operation of the hot gas by-pass. In thiscase, port S₄ is partly opened allowing the hot gases to be divertedalong line 314.

[0114]FIGS. 31a-31 c illustrate similar controls when theair-conditioning system is in the heating mode.

[0115] In the heating position illustrated in FIG. 31a, neither of theports S₄, S₅ are active but the expansion valve 315 is fully opened(shunts S₂, S₃ open) allowing the flow from shunt line 212 via expansionvalve 315 and shunt line 213.

[0116]FIG. 31b illustrates the valve member 304 moved slightly (counterclockwise) to partially close shunt port S₃ to the high pressure cavity224.

[0117]FIG. 31c illustrates the operation of the hot gas by-pass in theheating mode, wherein port S₅ is partly opened (s4 is closed) allowingthe hot gases to be diverted along line 316.

[0118] It will thus be seen that the novel valve assembly as describedabove may be used, not only as a change-over valve for changing from oneoperational mode to the other, but also as a control valve to perform alarge number of controls in either of the operational modes. Manyfeatures of the present invention contribute to this advantageousresult, particularly the construction of the valve member and theprovision of the annular high-pressure section around and enclosing thelow-pressure section, which self-regulates the valve member to produce athin air cushion facilitating moving the valve member while maintain itscontrol face, sufficiently close to the base to substantially isolatethe high-pressure section from the low-pressure section in any positionof the valve member. This construction of the valve member produces, ineffect, variable gates which can variably control leakage or shuntingfrom one pressure section to another (e.g. for temperature controlpurposes) or can variably control the cross-sectional area of thelow-pressure section exposed to the heat exchanger (e.g. for outputcontrol purposes), both without interrupting the operation of theair-conditioner. Further, the control of the pilot valve in any positionof the valve member also enables a small hot-gas bypass to be effectedwhenever desired and in any position of the valve member. Finally, usinga motor drive, particularly a step-motor, enables very precise control,both automatically and manually, of the valve member to perform any ofthe above-described functions.

[0119] Therefore, while the invention has been described with respect toseveral preferred embodiments, it will be appreciated that these are setforth merely for purposes of example, and that many other variations ofthe invention may be made. For example, the invention can be used inmanually-driven valve assemblies, or in valve assemblies forapplications other than in air-conditioning systems. Certain features ofthe invention could be used without other features. For example, one ormore of the above described control functions, e.g. leakage or shuntingcontrol, output control or pilot valve control, could be implemented inother change-over valve constructions.

[0120] It will be appreciated by persons skilled in the art that thepresent invention is not limited by what has been particularly shown anddescribed herein above. Rather the scope of the invention is defined bythe claims which follow:

1. A valve assembly for controlling the flow of a fluid between aplurality of ports including at least one high pressure port and one lowpressure port, comprising: a base mounting said plurality of ports; anda valve member rotatable to a plurality of operational positions withrespect to said base, said valve member having a control face facingsaid base to control the flow of fluid between said ports according tothe position of the valve member with respect to said base, and anopposite face facing away from said base; said control face of the valvemember being formed with a low pressure cavity in the central regionthereof, and with an annular high pressure cavity in the outer regionthereof completely circumscribing said low pressure cavity.
 2. The valveassembly according to claim 1, further comprising: a slow-acting ventfor applying high pressure from said high pressure cavity to saidopposite face of the valve member, when the valve member is in anoperational position, to firmly press the valve member into sealingcontact with the base, and thereby to isolate the high pressure cavityfrom the low pressure cavity; a pilot valve which is normally closed butselectively openable to release the high pressure applied to saidopposite face of the valve member, and thereby to enable the valvemember to be moved to another operational position; and a passagewayfrom said annular high pressure section of the valve member to saidopposite face of the valve member to maintain said control face of thevalve member sufficiently close to said base to substantially isolatethe high pressure cavity from the low pressure cavity also when saidpilot valve is open and said valve member is moved to anotheroperational position.
 3. The valve assembly according to claim 2,wherein said pilot valve, when opened, connects the high pressure atsaid opposite face of the valve member to said low pressure cavity torelease the high pressure applied to said opposite face of the valvemember.
 4. The valve assembly according to claim 2, further comprising:a rotary motor drive including an electrical motor, and a controlcircuit therefor for selectively moving the valve member from oneoperational position to another operational position in order tochange-over the connections between said high pressure and low pressureports, or to an intermediate position between said two operationalpositions in order to control the fluid flow with respect to said portswithout making a change-over of the connections between said highpressure and low pressure ports.
 5. The valve assembly according toclaim 4, wherein said control circuit controls said rotary motor driveto selectively move said valve member to any one of a plurality ofintermediate positions.
 6. The valve assembly according to claim 4,wherein said control face of the valve member is constructed such thatmoving the valve member to said intermediate position controls fluidleakage from said high pressure cavity to said low pressure cavity. 7.The valve assembly according to claim 4, wherein said control face ofthe valve member is constructed such that moving the valve member tosaid intermediate position controls the effective cross-sectional areaof said low pressure port exposed to said low-pressure cavity of thevalve member.
 8. The valve assembly according to claim 4, wherein saidrotary motor drive also controls said pilot valve to selectively open orclose it at any one of said operational or intermediate positions. 9.The valve assembly according to claim 8, wherein said rotary motor drivedrives said valve member via a coupling disk which is directly coupledto the rotary motor drive and is coupled to the valve member via alost-motion coupling such that the coupling disk may be rotated a smallamount to open or close the pilot valve without rotating the valvemember.
 10. The valve assembly according to claim 9, wherein saidcoupling disk includes a spring-biased pin receivable within a recess inthe valve member to releasably retain the coupling disk in a normalposition closing said pilot valve, but rotatable by said rotary motordrive with respect to said valve member to open or close said pilotvalve in any position of the valve member.
 11. The valve assemblyaccording to claim 9, wherein said coupling disk includes a pair ofdiametrically opposed spring-biased pins receivable withindiametrically-opposed recesses in the valve member to retain thecoupling disk in said normal position with respect to said pilot valve.12. The valve assembly according to claim 9, wherein said lost-motioncoupling between said coupling disk and said valve member comprises aprojection carried by said coupling disk movable within a slot in saidvalve member.
 13. The valve assembly according to claim 1, wherein saidcontrol face of the valve member is formed with a rib formationincluding inner and outer concentric, closed-loop ribs defining said lowpressure cavity within the inner closed-loop rib, and said high pressurecavity between the two closed-loop ribs.
 14. The valve assemblyaccording to claim 13, wherein said closed-loop ribs are shaped suchthat, at least at one intermediate position of the valve member betweenits two operational positions, said ribs partially shunt fluid from saidhigh pressure cavity to said low pressure cavity.
 15. The valve assemblyaccording to claim 13, wherein said closed-loop ribs are shaped suchthat, at least at one intermediate position of the valve member betweenits two operational positions, said ribs reduce the effectivecross-sectional area of the low pressure port exposed to said lowpressure cavity.
 16. The valve assembly according to claim 13, furthercomprising: at least one shunting port, and a shunting line from saidshunting port for partially shunting fluid away from one of saidcavities; said closed-loop ribs being shaped such that, at oneintermediate position of the valve member, said ribs partially shuntfluid away from said one cavity.
 17. The valve assembly according toclaim 16, wherein there are a shunting port and a shunting line for eachof said cavities, said closed loop ribs being shaped such that at eachof two different intermediate positions of the valve member, said ribspartially shunt fluid away from one of said cavities via one of saidshunting lines.
 18. The valve assembly according to claim 1, furthercomprising: a rotary motor drive, and a coupling disk for driving saidvalve member; said base and valve member being enclosed in ahermetically-sealed housing; said rotary motor drive being locatedexternally of said housing and coupled to said valve member by permanentmagnets carried on a driving disk located externally of said housing andcoupled to the rotary motor drive, and on a driven disk located withinsaid housing and coupled to the valve member.
 19. The valve assemblyaccording to claim 1, wherein said plurality of ports include a thirdport and a fourth port located on opposite sides of said high pressureport such that: in a first operational position of the valve member,said third port is connected to said low pressure port and said fourthport is connected to said high pressure port; and in a secondoperational position of the valve member, said third port is connectedto said high pressure port, and said fourth port is connected to saidlow pressure port.
 20. The valve assembly according to claim 19, incombination with: a compressor having a high pressure side connected tosaid high pressure port, and a low pressure side connected to said lowpressure port; a first heat exchanger connected to said third port; anda second heat exchanger connected to said fourth port; such that in oneoperational position of the valve member, the valve member connects saidfirst heat exchanger to said low pressure port, and said second heatexchanger to said high pressure port; and in an second operationalposition of the valve member, the valve member connects said first heatexchanger to said high pressure port and said second heat exchanger tosaid low pressure port.
 21. An air-conditioning system forair-conditioning an enclosed space by compressing and expanding a fluid,comprising: an inside heat exchanger to be located within the enclosedspace; an outside heat exchanger to be located outside the enclosedspace; a compressor having a low pressure side and a high pressure side;and a change-over valve including: a base having a low pressure portconnected to said low pressure side of the compressor, and a highpressure port connected to the high pressure side of the compressor; avalve member rotatable with respect to said base; a rotary motor drivefor driving said valve member; and a controller for controlling saidrotary motor drive to selectively drive said valve member; (a) to afirst operational position connecting said low pressure port to saidinside heat exchanger and said high pressure port to said outside heatexchanger to define a low pressure section including said inside heatexchanger for using the fluid to cool said enclosed space; and (b) to asecond operational position connecting said high pressure port to saidinside heat exchanger, and said low pressure port to said outside heatexchanger to define a high pressure section including said inside heatexchanger for using the fluid to heat said enclosed space; saidcontroller controlling said rotary motor drive for selectively drivingthe valve member to at least one further position, in addition to saidfirst and second operational positions; said valve member beingconstructed to maintain said high pressure section substantiallyisolated from said low pressure section and to perform at least oneadditional control function, when the valve member is driven to thefurther position.
 22. The air-conditioning system according to claim 21,wherein said at least one additional function is to shunt a part of thefluid from said high pressure port to said low pressure port to therebycontrol temperature within the air-conditioning system withoutinterrupting the operation of the compressor.
 23. The air-conditioningsystem according to claim 21, wherein said at least one additionalfunction is to restrict the effective cross-sectional area of said lowpressure port with respect to the heat-exchanger connected thereto, tothereby control the output of the air-conditioning system withoutinterrupting the operation of the compressor.
 24. The air-conditioningsystem according to claim 21, wherein said base includes a shunting portconnected to a shunting line; and wherein said at least one additionalfunction is to shunt a part of the fluid via said shunting line from ahigh pressure location to a low pressure location in theair-conditioning system, to thereby control temperature within theair-conditioning system without interrupting the operation of thecompressor.
 25. The air-conditioning system according to claim 24,wherein said base includes two shunting lines connected to two shuntingports, and said valve member selectively connects one shunting line tosaid inside heat exchanger, and the other shunting line to said outsideheat exchanger, according to the further position to which the valvemember is driven by the controller.
 26. The air-conditioning systemaccording to claim 21, wherein said change-over valve further includes apilot valve between said high pressure and low pressure ports; and saidcontroller selectively opens and closes said pilot valve at any positionof said valve member to control leakage from the high pressure port tosaid low pressure port for controlling temperature.
 27. Theair-conditioning system according to claim 21, wherein said valve memberincludes a control face facing said base to control the flow of fluidbetween said ports according to the position of the valve member withrespect to the base, and an opposite face facing away from said base;said control face of the valve member being formed with a low pressurecavity in the central region thereof, and with an annular high pressurecavity in the outer region thereof completely circumscribing said lowpressure cavity.
 28. The air-conditioning system according to claim 27,further comprising: a slow-acting vent for applying high pressure fromsaid high pressure cavity to said opposite face of the valve member,when the valve member is in an operational position, to firmly press thevalve member into sealing contact with the base, and thereby to isolatethe high pressure cavity from the low pressure cavity; a pilot valvewhich is normally closed but selectively openable to release the highpressure applied to said opposite face of the valve member, and therebyto enable the valve member to be moved to another operational position;and a passageway from said annular high pressure section of the valvemember to said opposite face of the valve member to maintain saidcontrol face of the valve member sufficiently close to said base tosubstantially isolate the high pressure cavity from the low pressurecavity also when said pilot valve is open and said valve member is movedto another operational position or to a said further positionintermediate said first and second operational positions.
 29. Theair-conditioning system according to claim 27, wherein said control faceof the valve member is formed with a rib formation including inner andouter concentric closed-loop ribs defining said low pressure cavitywithin the inner closed-loop rib, and said high pressure cavity betweenthe two closed-loop ribs.
 30. The air-conditioning system according toclaim 29, wherein said closed loop ribs are shaped such that, at leastat one intermediate position of the valve member between said first andsecond operational positions, said ribs partially shunt fluid from saidhigh pressure cavity to said low pressure cavity.
 31. Theair-conditioning system according to claim 29, wherein said closed-loopribs are shaped such that, at least at one intermediate position of thevalve member between said first and second operational positions, saidribs reduce the effective cross-sectional area of the low pressure portexposed to said low pressure cavity.
 32. The air-conditioning systemaccording to claim 29, further comprising: at least one shunting port,and a shunting line from said shunting port for partially shunting fluidaway from one of said cavities; said closed-loop ribs being shaped suchthat, at one intermediate position of the valve member between saidfirst and second operational positions, said ribs partially shunt fluidaway from said one cavity.
 33. The air-conditioning system according toclaim 32, wherein there are a shunting port and a shunting line for eachof said cavities, said closed loop ribs being shaped such that at eachof two different intermediate positions of the valve member between saidfirst and second operational positions, said ribs partially shunt fluidaway from one of said cavities via one of said shunting lines.
 34. Theair-conditioning system according to claim 21, wherein said controllerincludes a temperature sensor for sensing the temperature at apredetermined location within the air-conditioning system and forcontrolling said rotary motor drive in response to the sensedtemperature.
 35. An air-conditioning system for air-conditioning anenclosed space by compressing and expanding a fluid, comprising: aninside heat exchanger to be located within the enclosed space; anoutside heat exchanger to be located outside the enclosed space; acompressor having a low pressure side and a high pressure side; and achange-over valve including: a base having a low pressure port connectedto said low pressure side of the compressor, a high pressure portconnected to the high pressure side of the compressor, and at least oneshunting port connected to a shunting line; a valve member rotatablewith respect to said base; a rotary motor drive for driving said valvemember; and a controller for controlling said rotary motor drive toselectively drive said valve member; (a) to a first position connectingsaid low pressure ports to said inside heat exchanger, and said highpressure port to said outside heat exchanger, to define a low pressuresection including said inside heat exchanger for using the fluid to coolsaid enclosed space; (b) to a second position connecting said highpressure port to said inside heat exchanger and said low pressure portto said outside heat exchanger, to define a high pressure sectionincluding said inside heat exchanger for using the fluids to heat saidenclosed space; and (c) at least one further position connecting saidshunting port to shunt a part of the fluid via said shunting line from ahigh pressure location to a low pressure location in theair-conditioning system to control temperature within theair-conditioning system without interrupting the operation of thecompressor.
 36. The air-conditioning system according to claim 35,wherein said change-over valve further includes a pilot valve betweensaid high pressure and low pressure ports; and said controllerselectively opens and closes said pilot valve at any position of saidvalve member to control leakage from the high pressure port to said lowpressure port.
 37. The air-conditioning system according to claim 35,wherein said valve member includes a control face facing said base tocontrol the flow of fluid between said ports according to the positionof the valve member with respect to the base, and an opposite facefacing away from said base; said control face of the valve member beingformed with a low pressure cavity in the central region thereof, andwith an annular high pressure cavity in the outer region thereofcompletely circumscribing said low pressure cavity.
 38. Theair-conditioning system according to claim 37, further comprising: aslow-acting vent for applying high pressure from said high pressurecavity to said opposite face of the valve member, when the valve memberis in an operational position, to firmly press the valve member intosealing contact with the base, and thereby to isolate the high pressurecavity from the low pressure cavity; a pilot valve which is normallyclosed but selectively openable to release the high pressure applied tosaid opposite face of the valve member, and thereby to enable the valvemember to be moved to another operational position; and a passagewayfrom said annular high pressure section of the valve member to saidopposite face of the valve member to maintain said control face of thevalve member sufficiently close to said base to substantially isolatethe high pressure cavity from the low pressure cavity also when saidpilot valve is open and said valve member is moved to anotheroperational position or to said further position.
 39. Theair-conditioning system according to claim 37, wherein said control faceof the valve member is formed with a rib formation including inner andouter concentric closed-loop ribs defining said low pressure cavitywithin the inner closed-loop rib, and said high pressure cavity betweenthe two closed-loop ribs.
 40. The air-conditioning system according toclaim 39, wherein said closed-loop ribs are shaped such that, at leastat one further position of the valve member intermediate its twooperational positions, said ribs partially shunt fluid from said highpressure cavity to said low pressure cavity.
 41. The air-conditioningsystem according to claim 39, wherein said closed-loop ribs are shapedsuch that, at least at one further position of the valve memberintermediate its two operational positions, said ribs reduce theeffective cross-sectional area of the low pressure port exposed to saidlow pressure cavity.
 42. An air-conditioning system for air-conditioningan enclosed space by compressing and expanding a fluid, comprising: aninside heat exchanger to be located within the enclosed space; anoutside heat exchanger to be located outside the enclosed space; acompressor having a low pressure side and a high pressure side; and achange-over valve including: a base having a low pressure port connectedto said low pressure side of the compressor, and a high pressure portconnected to the high pressure side of the compressor; a valve memberrotatable with respect to said base; a pilot valve connecting the highpressure port to the low pressure port of the change-over valve; arotary motor drive for driving said valve member; and a controller forcontrolling said rotary motor drive to selectively drive said valvemember; said controller also controlling said pilot valve to selectivelyopen or close it in any position of the valve member to produce acontrolled leakage from said high pressure side to said low pressureside of the compressor.
 43. The air-conditioning system according toclaim 42, wherein said rotary motor drive drives said valve member via acoupling disk which is directly coupled to the rotary motor drive and iscoupled to the valve member via a lost-motion coupling such that thecoupling disk may be rotated a small amount to open or close the pilotvalve without rotating the valve member.
 44. The air-conditioning systemaccording to claim 43, wherein said coupling disk includes aspring-biased pin receivable within a recess in the valve member toreleasably retain the coupling disk in a normal position closing saidpilot valve, but rotatable by said rotary motor drive with respect tosaid valve member to open or close said pilot valve in any position ofthe valve member.
 45. The air-conditioning system according to claim 43,wherein said coupling disk includes a pair of diametrically opposedspring-biased pins receivable within diametrically-opposed recesses inthe valve member to retain the coupling disk in a normal position withrespect to said pilot valve.
 46. The air-conditioning system accordingto claim 43, wherein said lost-motion coupling between said couplingdisk and said valve member comprises a projection carried by saidcoupling disk movable within a slot in said valve member.
 47. A methodof air conditioning an enclosed space, comprising: providing an airconditioning system according to claim 21; and selectively actuatingsaid valve assembly; (a) to said first operational position to effect acooling mode of operation; (b) to said second operational position toeffect a heating mode of operation; or (c) to said at least one furtherposition, to produce a control of the air-conditioning system in therespective mode of operation without interrupting the operation of theair-conditioning system.
 48. The method according to claim 47, whereinsaid valve assembly is actuated to said further position to produce acontrolled leakage between said high pressure port to said low pressureport to prevent frosting without interrupting the operation of theair-conditioning system.
 49. The method according to claim 48, whereinthe ambient temperature is sensed by a temperature sensor, and theoutput of said temperature sensor is used to automatically control thevalve assembly to prevent frosting by actuating the valve from oneoperational position to said further position.
 50. The method accordingto claim 47, wherein said valve assembly is actuated to said furtherposition to produce a controlled reduction in the cross-sectional areaof said low pressure port in the base to reduce the output of theair-conditioning system without interrupting its operation.
 51. Themethod according to claim 47, wherein said change-over valve includes apilot valve, and said controller selectively opens or closes said pilotvalve at any one of said operational or further positions to produce acontrolled leakage from the high pressure side to the low pressure sideof the compressor for temperature control purposes.
 52. The methodaccording to claim 47, wherein said base includes a shunting portconnected to a shunting line, and said rotary motor drive is controlledto selectively connect said shunting line to shunt a part of the fluidvia said shunting port from a high pressure location to a low pressurelocation in the air-conditioning system to control temperature withinthe air-conditioning system without interrupting the operation of thecompressor.
 53. The valve assembly according to claim 19, furthercomprising: a first shunting port and a first shunting line from saidfirst shunting port and second shunting port and a second shunting linefrom said second shunting port for at least partially shunting fluidaway from one of said cavities via one of said shunting lines.
 54. Thevalve assembly according to claim 53, wherein said pilot valve is anexpansion valve which when opened, connects the high pressure at saidopposite face of the valve member to said low pressure cavity to releasethe high pressure applied to said opposite face of the valve member. 55.The valve assembly according to claim 54, in combination with: acompressor having a high pressure side connected to said high pressureport, and a low pressure side connected to said low pressure port; afirst heat exchanger connected to said third port; and a second heatexchanger connected to said fourth port; wherein said valve memberconnects said first heat exchanger to said low pressure port, and saidsecond heat exchanger to said high pressure port; and such that, in oneoperational position of the valve member, the direction of flow is fromsaid first heat exchanger to said second heat exchanger and in a secondoperational position of the valve member, the direction of flow is fromsaid second heat exchanger to said first heat exchanger.
 56. Theair-conditioning system according to claim 29, further comprising: afirst shunting port and a first shunting line from said first shuntingport and second shunting port and a second shunting line from saidsecond shunting port for at least partially shunting fluid away from oneof said cavities via one of said shunting lines.
 57. Theair-conditioning system according to claim 56, wherein said pilot valveis an expansion valve which when opened, connects the high pressure atsaid opposite face of the valve member to said low pressure cavity torelease the high pressure applied to said opposite face of the valvemember.
 58. The air-conditioning system according to claim 42, furthercomprising: a first shunting port and a first shunting line from saidfirst shunting port, and second shunting port and a second shunting linefrom said second shunting port for at least partially shunting fluidaway from one of said cavities via one of said shunting lines.
 59. Themethod according to claim 47, wherein said change-over valve includes anexpansion valve, and said controller selectively opens or closes saidexpansion valve at any one of said operational or further positions todirect the flow of gasses from said first heat exchanger to said secondheat exchanger or vice versa.
 60. The method according to claim 47,wherein said base includes a first shunting port and a first shuntingline from said first shunting port, and second shunting port and asecond shunting line from said second shunting port for at leastpartially shunting fluid away from one of said cavities via one of saidshunting lines.
 61. The method according to claim 47, wherein said firstoperational position includes the step of actuating said valve assemblythereby to divert gasses from said first shunting port via said firstshunting line, and said second operational position includes the step ofactuating said valve assembly thereby to divert gasses from said secondshunting port via said second shunting line.